1. Field of the Invention
This invention relates to an electronic camera for magnetically recording still image signals and, more particularly, to such a camera that is conditioned to carry out a recording operation just prior to performing the operation itself, thereby minimizing power consumption during long periods when such conditioning is not necessary.
2. Description of the Prior Art
So-called electronic still cameras have been introduced in which video signals are generated in response to a sensed image and recorded on a magnetic medium, such as a miniaturized floppy disk. Video picture signals produced when the recorded video signals are played back, may be displayed on a monitor, such as a conventional television receiver, or may be "printed" to form a "hard copy" image corresponding thereto.
To effect a magnetic recording of the image signals, the floppy disk or other magnetic medium must be moved past a magnetic transducer, or head. Typically, the magnetic medium is rotated by a spindle which, in turn, is driven by a spindle drive motor. When compared to the power consumption of the various solid state circuits included in the camera, the spindle drive motor exhibits relatively high power consumption. Furthermore, since the motor is a mechanical device with measurable inertia, a period of time is needed from the moment that the motor is supplied with energy until it reaches a satisfactory rotary speed suitable for the magnetic recording of image signals.
Electronic cameras which have been proposed heretofore normally are provided with a main power on/off switch. When this switch is OFF, operating energy is not supplied to the various drive motors and circuits included in the camera. However, even when the switch is ON, it may not be necessary to supply operating energy to those drive motors or to the image pick up elements and the signal recording circuitry unless and until a picture taking operation (which, in an electronic camera is more accurately referred to as a recording operation) actually is carried out. To energize the motors long before an image is to be recorded is an unnecessary consumption of power. Since the preferred source of energy for an electronic camera is a battery, it is important not to deplete that battery unnecessarily. Consequently, during quiescent, or standby modes of the camera, energy normally is not supplied to the drive motors or to many of the camera circuits even though main on/off switch is ON.
One proposal to conserve energy in an electronic camera of the forementioned type is described in Japanese laid open patent application No. 58-33370 (filed as Japanese application 56-131933). In that proposed camera, two separate switches are actuated in sequence so as to: (1) first initialize the drive motors, pick up elements and recording circuitry--that is, first supply operating energy to those motors to bring them up to speed and apply power to the pick up elements and recording circuitry; and then (2) execute an image recording operation. The latter operation is performed by reading out one field or frame of electrical image signals produced by a suitable sensor, such as a CCD sensor, in response to an optical image projected thereto, and magnetically recording the field or frame of signals.
Typically, the separate switches are sequentially operated by a single operating element which, when normally actuated by a user, moves to first and second positions corresponding to the aforementioned initializing and recording operations. When the operating element moves to its first position, the camera is initialized and thus made ready to record images signals; and when the operating element moves to its second position, the image signals are recorded. Thus, energy is not unnecessarily supplied to power consuming elements and devices until the operating element moves to its first position even though the main power on/off switch may be ON.
Although, this arrangement minimizes power consumption, it suffers from a significant disadvantage and drawback. Usually, the operating element is constructed as a spring-biased shutter release button. When that button is partially depressed, corresponding to the aforementioned first position, the camera is initialized. When that button is fully depressed, corresponding to the aforementioned second position, the image recording operation is carried out. In many instances, then, while the user is composing a "picture" to be recorded, he will partially depress the shutter release button to be ready to record a desired image instantly. However, there is a fine distinction between the partially and fully depressed positions of the shutter release button. In attempting merely to depress the shutter release button partially, the user may inadvertently depress that button fully. Still further, even when the user successfully locates the partially depressed position of the shutter release button, a suitable force nevertheless must be exerted to maintain the button in that position. This could be tiresome. But to reduce the force necessary to maintain the shutter release button partially depressed may result in the unintentional release of that button, thus de-initializing the camera. Consequently, the user may miss a desirable photographic opportunity because the camera may no longer be initialized for recording.